Compatibility with FTP clients allows services to be available and compatible with existing infrastructures of existing clients and potential customers with infrastructure that rely on or utilize the FTP protocol. By further utilizing multiple FTP servers to support client or user needs, redundancy and automatic failover for an FTP server can be provided as an enhancement feature by removing a single point of failure.
However, the difficulty in load balancing a secure FTP session stems from the fact that it uses multiple TCP ports for a given session (e.g., one connection is for control whereas another connection is used for data transfer). While unencrypted or unsecured FTP packets in plain text can be inspected and the two connections can be paired up, encrypted or otherwise secure FTP connections cannot be matched for routing to the same backend FTP server. Some solutions for load balancers to handle secure FTP connections include requiring the hardware load balancer to terminate the SSL connection. However, this solution is highly un-scalable and can cause performance issues due to the workload imposed on the load balancers.